The article presents the results of preventive examination of 577 073 children aged 0 to 17 in the Republic of Tatarstan in 2013-2015. It demonstrates distribution of children of decree ages into health groups. The following results have been obtained: quantity of healthy children amounts to 13,3%, quantity of children with chronic pathology amounts to 12,9%. Before admittance to school 13,9% of children considered to be in the first health group, at the end of the first school year the amount of healthy children decreased to 13,2%, when the subject study started the amount decreased to 13.0%, before graduation from school there 11,0% of healthy children. Respectively there is an increased amount of children with chronic pathology (III- V health groups). It changes from 10,3% before admittance to school to 19,7% of graduating children. Therefore, we can arrive at a conclusion, that during the school study time the health of children becomes worse.